Given three integers as user inputs that represent the number of bottles of drinks to purchase, to restock, and to purchase afterward, create a VendingMachine object that performs the following operations:

Purchase the first input number of bottles of drinks

Restock the second input number of bottles of drinks

Purchase the last input number of bottles of drinks

Report inventory

A VendingMachine's initial inventory is $20$ bottles of drinks.

Ex: If the input is:

$5$

$2$

$7$

the output is:

Inventory: $10$ bottles